The missile was approaching fast and gathering speed on a column of flame. Inside a trailer, miles away, it appeared on the radar screen of a soldier on-watch. From its radar signature, he realized it was a Katyusha, a ten-foot long missile launched from a truck and capable of delivering a powerful explosive charge or chemical weapon. Acting quickly, he commanded a device resembling a large spotlight mounted on the roof of the trailer to whir into motion. After panning for a few moments, the device locked onto the distant rocket arching overhead. It shot an invisible high-energy laser beam into the side of the Katyusha, following the target even as it continued to fly at several times the speed of sound. Seconds later, the missile exploded into a ball of flame, disintegrating into shards which rained harmlessly onto the desert below.

Is this a scene taken from a science fiction story? Not at all. Instead, it's a description of an actual test which took place over three years ago of the Tactical High Energy Laser (THEL), developed by the U.S. Army in a joint project with the Government of Israel. Laser weapons are not just the stuff of Buck Rogers any more, and the THEL program is just a small component of a multi-billion dollar effort by the U.S. military to introduce laser weapons to the battlefield. Within ten years, the U.S. military plans to mount powerful laser weapons on tanks, Humvees, fighter jets, and other aircraft. Research is even underway to develop a Humvee-mounted non-lethal microwave energy weapon capable of incapacitating people by causing severe pain. If these efforts are successful, energy weapons will revolutionize warfare in the 21st century.

A diagram showing how the THEL system works. Credit: US Army Space & Missile Command.

Energy weapons are yet another example of science fiction making the leap to science fact. But what will these energy weapons really be like, what can they really do, and when will they enter real combat? How does the emerging reality of energy weapons compare to their portrayal in fictional stories? Have authors of speculative fiction guessed right, or is this technology even stranger than they imagined?

A Primer on Lasers

Lasers have become commonplace in our society. Hand-held laser pointers used for presentations can be purchased at standard office supply stores. Lasers are used widely in printers and CD-players. They are used to perform eye surgery or to cut patterns into fabric for clothing. Military personnel, law enforcement, and sport shooters have also used lasers for many years as targeting aids for weapons. The list of useful applications for lasers goes on, and grows every day.

The amount of energy laser weapons use separates them from lasers installed in everyday appliances. Laser weapons require a tremendous input of energy, ranging from tens of kilowatts to tens of megawatts.

The U.S. military plans to develop both solid-state and chemical lasers into weapon systems. Solid-state lasers pass electricity through a solid medium of crystal or glass, such as a ruby rod. They require only electrical current to operate, can easily be reset for additional firings, and are relatively inexpensive to fire. If mounted on a vehicle as a weapon, the electrical energy for a solid-state laser could be provided by batteries recharged by the vehicle's engine. Cooling a solid-state laser weapon presents a major challenge, however. Solid-state lasers powerful enough for weapons use are currently only 1% efficient, and over the next decade, will probably improve to only 10% efficiency, at best. Anywhere from 90-99% of the input power remains as heat in the laser body. This heat must be dissipated before it melts the laser into a useless pile of slag.

As the name suggests, chemical lasers rely on a chemical reaction, and not electricity, to generate energy. Besides heat, the reaction releases an intense burst of infrared radiation, which is focused into a beam by the laser. Chemical lasers can pack a tremendous amount of energy (far greater than that produced by solid-state lasers), but create a highly corrosive and toxic chemical end-product. They also require large volumes of reactant chemicals to operate, making them difficult to transport and relatively expensive to fire compared to solid-state lasers.

If used as weapons, all lasers share a common problem: air. Air turbulence scatters laser beams, and this is a particular problem for aircraft-mounted lasers. Cloud cover, fog, or dust storms can also interfere with laser beams. Air conditions limit the effective range of lasers in the atmosphere. Researchers have applied a new technology called adaptive optics to the problem of air turbulence. Adaptive optics has in large part enabled the emergence of lasers for weapon applications, and is described in further detail below.

If technical challenges can be surmounted, lasers may be used in the future as nearly impenetrable systems to intercept missiles or as terrifying offensive weapons. It's not hard to imagine their potential in either case. Attacking at the speed of light (186,000 miles per hour), lasers will be nearly impossible to dodge.

The Tactical High Energy Laser

No laser weapon system has achieved greater success than the THEL. The THEL mixes deuterium (a form of hydrogen) with fluorine to create deuterium fluoride, generating an intense burst of infrared radiation in the process. To date, the THEL is the only laser to successfully intercept and destroy a moving target.

The THEL program was initiated in 1996 as a cooperative project between the U.S. and Israel after a devastating series of Katyusha rocket attacks launched by Hezbollah into Israel from southern Lebanon. The U.S. military had funded basic research leading up to the THEL program for 25-30 years previously, however. Israel eventually plans to deploy a version of the THEL system to protect its borders from short-range rocket attacks. During tests in 2000, the THEL successfully shot down 26 out of 30 Katyusha rockets, including a salvo of rockets launched simultaneously. This demonstration was significant because Katyushas are extremely small, fast targets. In November 2002, the THEL successfully intercepted and destroyed an artillery shell, an even more elusive target.

An image of the actual THEL system used in testing. Credit: US Army Space & Missile Command.

Although the per-shot chemical costs of the THEL system (about $3,000) are relatively high compared to solid-state lasers, they are a small fraction of the cost of interceptor missiles such as the Patriot (about $3.8 million each). The primary disadvantage of THEL, as with all chemical lasers, is the enormous size of the system. It takes three trailer-sized containers to fit the THEL. The U.S. military is currently focusing on making the THEL system smaller and more transportable. They hope to deploy a mobile version of the THEL (called MTHEL) by 2007.

The Airborne Laser

Aside from large, fixed, ground-based laser systems like the THEL, the U.S. military is spending billions to develop laser weapons small and light enough to fit on vehicles, including airplanes. The largest system currently under development is the Airborne Laser (ABL), a heavily modified Boeing 747 freighter aircraft with a nose-mounted rotating turret containing a chemical oxygen iodine laser. The system mixes chemicals found in common household cleaners, such as bleach and Drano, to create an invisible laser beam with a devastating power output of up to two megawatts (enough power to run a small town). Each 747 will store enough reactants for about 20 shots before refueling. This laser will be considerably more powerful than the THEL, capable of shooting down large missiles, such as SCUDs, from hundreds of miles away. There's also talk about using ABL to shoot down enemy planes.

The breakthrough that made ABL possible was not in chemical laser technology, which has been around since before the Vietnam War. Instead, it's a technology called adaptive optics. Atmospheric turbulence, caused by fluctuations in air temperature, scatters and weakens all laser beams, making it difficult to target a laser on a small, distant, moving target. Adaptive optics, originally developed to improve the images taken by ground-based astronomical telescopes, uses a deformable (sometimes called a "rubber") mirror to keep the laser beam in focus. The mirror has hundreds of actuators attached to it, capable of moving thousands of times a second to change its shape.

The U.S. Missile Defense Agency runs the $1.6 billion ABL program. A team composed of the nation's three biggest defense contractors -- Boeing, Lockheed Martin, and Northrop Grumman -- is building the ABL. The program has progressed well beyond the paper design phase. Except for installation of the laser, Boeing has completed modifications to the 747, including the nose turret. Northrop Grumman, the actual developer of the laser, conducted a successful test firing of the laser last year at 118 percent of its design power. The laser will be installed in the turret sometime this year. The team plans to conduct a full-scale ABL test, shooting down SCUD missiles in flight, sometime by the end of 2004. If all goes as planned, the Air Force hopes to build a fleet of seven ABL aircraft to deploy at short notice to trouble spots around the world.

The ABL program is not without its detractors. The ABL will emit corrosive gases produced by the laser into the atmosphere, raising concerns from environmentalists. Other skeptics are unconvinced that the ABL will be capable of focusing a beam on a missile hundreds of miles away with enough power to actually destroy it.

The Advanced Tactical Laser

The ABL is the 800-pound gorilla at the Pentagon's laser weapons cocktail party. The Pentagon is also funding a much smaller program called the Advanced Tactical Laser (ATL) to develop chemical lasers for small aircraft and helicopters. Although the ATL uses the same basic technology as the ABL (chemical oxygen-iodine lasers and adaptive optics), it does so on a comparatively minuscule scale. The prototype ATL will have a power output of 70 kilowatts, more than an order of magnitude lower than the ABL, but still high enough to inflict serious damage. The laser focuses a 4-inch wide spot on its target carrying enough energy to melt through steel. The prototype ATL will be capable of delivering a laser beam for a maximum of about 40 seconds before expending all of its chemicals.

The Pentagon will invest more than $180 million in the ATL program through 2006. The Boeing Company is the program's prime contractor. By 2006, Boeing plans to install and test a prototype ATL on a C-130, a fixed-wing, propeller-driven aircraft. The ATL will be a sealed system mounted on a pallet, generating no chemical exhaust. The pallet, placed inside the cargo bay of the C-130, will be 15 feet long and 6 feet wide. It will weigh about 4 tons, or as much as a large-size SUV. It will fire through either an opening or a turret in the fuselage of the aircraft.

If successful, the Air Force and Army plan to put ATLs on other aircraft, including the C-47 attack helicopter, or the tilt-wing V-22 "Osprey." Unlike the ABL, the U.S. military will use the ATL primarily as an offensive weapon against non-armored vehicles and fixed structures, such as enemy radar antennas or radio towers, up to 10 miles away. It will have a targeting precision accurate enough to blow the tires off a truck from miles away without damaging any other part of the vehicle.

The Search for Solid-State

While chemical lasers definitely win the prize for sheer firepower, the need to cart around and eventually dispose of huge quantities of corrosive chemicals in order to operate these systems has led the U.S. military to also look at the potential of solid-state lasers. As described earlier, solid-state lasers require only electricity and produce no waste products. As long as the laser is cooled and the electricity keeps flowing, they can fire indefinitely.

In September 2002, the Air Force Research Laboratory (AFRL) launched a $49 million program to develop a small, 25-kilowatt solid-state laser weapon by the end of 2004. If this initial effort is successful, they hope to develop a 100-kilowatt version by the end of the decade, capable of being installed on tanks, Humvees, fighter jets, or ships. In particular, the Air Force hopes to install a 100-kilowatt solid-state laser on a version of the new F-35 Joint Strike Fighter. On the drawing boards are "fotofighters," new classes of small fighter jets employing laser weapons exclusively. The AFRL thinks these lasers would be capable of hitting targets 30 to 155 miles away. Electrical power for the laser would be drawn from the spinning motion of the jet's turbines, a byproduct of producing thrust. The AFRL has even modified F-16 fighter jet simulators to train pilots on the capabilities of lasers. These simulators are being used to develop the tactics and techniques for future laser combat.

How much damage would a 25 or 100-kilowatt solid-state laser cause? So far, the most powerful solid-state laser, located at the White Sands Missile Range, produces an average power output of 10 kilowatts. It can deliver 500-joule laser pulses 20 times a second for 10-second bursts. This laser can burn a 1-centimeter diameter hole through a 2-centimeter thick stack of steel plates in six seconds, using just 30 cents worth of electricity from a wall outlet. A 25 or 100-kilowatt system would do considerably more damage.

Energy efficiency and heat rejection are the key technical challenges any solid-state laser weapons program must overcome. The 10-kilowatt laser at White Sands requires 1 megawatt of input power, achieving only 1% efficiency. A 100-kilowatt laser must achieve 10% efficiency, requiring 1 megawatt of input power (the energy consumption of 1,000 average U.S. suburban homes) to be a feasible mobile weapon system.

Using the laser at White Sands as a testbed, the U.S. Army is funding its own effort to develop a 100-kilowatt solid-state laser weapon. Ultimately, they think the laser will work off batteries and measure 2 meters in length and 1 meter in width. It would be mounted on top of a hybrid-electric Humvee. Its batteries would be recharged by the Humvee's diesel engine. The team is also working on a targeting system using adaptive optics. They think the system would be capable of disabling targets up to 10 kilometers away. The laser-equipped Humvee would be used primarily to intercept short range artillery, rockets, and mortars launched by an enemy. Their goal is to demonstrate the full 100-kilowatt Humvee system by 2007.

The Ultimate Way to Clear a Room

Lasers are not the only energy weapons the U.S. military hopes to develop within the next decade. Over the last ten years, the AFRL has also invested $40 million in a bizarre non-lethal weapon they've given the seemingly innocuous name "Active Denial Technology." These anti-personnel devices fire beams of microwaves at targets up to 700 yards away, penetrating just underneath the skin and heating the tissue below to 130 degrees Fahrenheit, inducing severe pain in the process. For anyone who thankfully has never been inside a microwave oven in operation, the pain induced has been compared to touching a hot light bulb. It's quietly undergoing testing at AFRL on animals and intrepid human volunteers. According to the AFRL, it causes no permanent tissue damage. They envision deploying this technology widely for use in riot control and peacekeeping missions.

Reportedly, Active Denial Technology systems are very close to full operational deployment. The U.S. military believes they can fit an operational version of this device on the back of a Humvee. The Humvee would enter a trouble spot in advance of ground troops or police, using the microwave beam to clear the path of enemies or mobs.

Lethal Lasers and the Law

In advocating to Congress for increased funding for energy weapons development, the Pentagon has been careful to stress the defensive capabilities of the technology. For political reasons, almost all the systems currently under development are expressly for intercepting incoming missiles or artillery. Highlighting the lethality of these weapons won't win many votes on Capitol Hill for multi-billion programs. The devastating potential of lasers as offensive weapons cannot be lost on military planners, however. A laser capable of tracking and destroying an accelerating missile traveling at many times the speed of sound can also effectively shoot down virtually any aircraft, and will undoubtedly be used for that purpose someday. The first generation of "fotofighters" will no doubt be used to destroy enemy tanks, artillery positions, and other aircraft. Humvee-mounted laser cannons will be used to disable tanks and aircraft from miles away, not to mention what they'll do to the human body when turned against enemy soldiers.

Currently, no international law exists banning the lethal use of lasers. The International Committee of the Red Cross did rule in 1998 that a ban exists (under Protocol IV of the 1980 Convention on Conventional Weapons) against lasers designed specifically to cause permanent blindness, but none of the laser weapon programs described in this article falls into that category. The blinding laser ban also does not ban other non-lethal energy weapons, like the so-called Active Denial Technology.

Fact versus Fantasy

How does the emerging reality compare to conceptions of energy weapons portrayed in speculative fiction?

Science fiction stories almost invariably portray laser weapons as solid-state devices, requiring only electrical energy to operate. This applies to both "soft" science fiction (e.g., Star Wars or Star Trek) and "hard" science fiction (e.g., Larry Niven and Jerry Pournelle's The Mote in God's Eye, or Vernor Vinge's A Deepness in the Sky). In reality, the first working laser weapons are not solid-state systems, but chemical. When they do emerge, solid-state laser weapons will have power outputs and damage potential orders of magnitude lower than chemical lasers for the foreseeable future. Despite this fact, chemical lasers receive very little treatment in speculative fiction. One notable example is Dale Brown's Dreamland: Razor's Edge, a recently published novel by Dale Brown, a former Captain in the U.S. Air Force. He no doubt drew inspiration from the success of the THEL program in crafting this novel, which involves (as described on the back cover), "a mobile chemical laser system [nicknamed 'Razor'] with a range of 600 kilometers capable of downing anything that flies."

The look of laser beams also subtly differs between fact and fiction. While some solid-state lasers do produce beams in visible wavelengths, most lasers considered for weapons use (including all chemical lasers) produce infrared beams invisible to the human eye. They are a far cry from the flashy laser blasts shown in science fiction movies and television series.

One treatment of laser technology in both "soft" and "hard" science fiction -- the handheld ray gun -- has definitely not emerged, and arguably may never emerge. The smallest laser weapons under development barely fit on Humvees and weigh thousands of pounds, including the energy storage system. Even if engineers produce a battery with sufficiency high energy-density to fit into a handheld weapon, lasers will convert only a fraction of the input energy (perhaps 10-30% at best) into laser output power. The remainder will take the form of heat, rendering a handheld gun red-hot to the touch.

Although handheld laser weapons may remain a fantasy forever, based on foreseeable advances in technology, a rifle-sized solid-state laser weapon may exist in the far, far future. Heat coils wrapped around the rifle barrel might cool the system after firings. A cord leading from the rifle might connect to a large backpack containing the electric generator and the cooling system, complete with large radiators to dissipate the heat. The user would probably need to wear a thick thermal protection suit, however.

Closing Thoughts

If the Pentagon has its way, energy weapons will be widespread among U.S. armed forces in the near future. U.S. military conflicts have become material for prime-time television, so in as little as ten years, television viewers worldwide might be watching as directed energy weapons see combat for the first time. Once that happens, readers and writers of speculative fiction will need to change their preconceived notions of energy weapons garnered from stories. More importantly, their development will significantly change warfare forever.

Strange Horizons is a weekly magazine of and about speculative fiction. We publish fiction, poetry, reviews, essays, interviews, and art. For more information, see our about page. All material in Strange Horizons is copyrighted to the original authors and may not be reproduced without permission.